We plan to characterize the molecular nature of the tumor associated antigens involved in the stimulation of syngeneic lymphocytes. Both 3H-thymidine incorporation nd cell mediated cytotoxicity will be measured. The tumor system that will be used is the spontaneous reticulum cell sarcoma of SJL/J mice. In addition to the bioassays used, we plan to isolate antigens by co-precipitation with nonspecific antisera and separation on SDS gel electrophoresis. Furthermore, in some instances peptide mapping of isolated molecules will be undertaken. The relationship between antigens isolated from normal and neoplastic cells will be established.